Cardiac Muscle Structure
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Questions and Answers

What is the normal value of stroke volume when the heart rate is normal?

  • 80 mL
  • 70 mL (correct)
  • 90 mL
  • 50 mL

    • Which of the following techniques is used to measure cardiac output?

  • Phonocardiography
  • Electrocardiography
  • Radiocardiography
  • Thermodilution technique (correct)

    • What is the term for a heart rate above 100/minute?

  • Tachycardia (correct)
  • Bradycardia
  • Cardiac arrest
  • Arrhythmia

    • What is the normal value of cardiac index?

    <p>2.8 ± 0.3 liters/ square meter of body surface area/ minute</p> Signup and view all the answers

    What is the term for the amount of blood pumped from each ventricle in one minute?

    <p>Minute volume</p> Signup and view all the answers

    Which of the following conditions is a pathological condition when tachycardia occurs?

    <p>Fever</p> Signup and view all the answers

    What is the normal heart rate in an adult?

    <p>60-80 per minute</p> Signup and view all the answers

    What is the term for the classification of cardiac murmur produced during systole of the heart?

    <p>Systolic murmur</p> Signup and view all the answers

    What is the normal range of systolic blood pressure?

    <p>110-140 mm Hg</p> Signup and view all the answers

    What is the term for the difference between systolic pressure and diastolic pressure?

    <p>Pulse pressure</p> Signup and view all the answers

    Which of the following is a physiological condition when bradycardia occurs?

    <p>Athletic heart</p> Signup and view all the answers

    What is the normal range of diastolic blood pressure?

    <p>60-80 mm Hg</p> Signup and view all the answers

    What is the effect of meals on arterial blood pressure?

    <p>It increases for few hours</p> Signup and view all the answers

    What is the effect of sleep on arterial blood pressure?

    <p>It reduces up to 15 to 20 mm Hg</p> Signup and view all the answers

    Which of the following is a pathological condition when bradycardia occurs?

    <p>Hypothyroidism</p> Signup and view all the answers

    What is the term for the lateral pressure exerted by the column of blood on the wall of arteries?

    <p>Arterial blood pressure</p> Signup and view all the answers

    Which condition is associated with a loud, audible third heart sound?

    <p>Cardiac Failure</p> Signup and view all the answers

    What is the term used to describe the sound when a third heart sound is heard by a stethoscope?

    <p>Triple Heart Sound</p> Signup and view all the answers

    What is the primary reason for the production of a cardiac murmur?

    <p>Rapid blood flow through a narrowed valve</p> Signup and view all the answers

    Which of the following is NOT a method used to study heart sounds?

    <p>Electrocardiogram (ECG)</p> Signup and view all the answers

    What is the primary cause of a fourth heart sound?

    <p>Ventricular stiffness</p> Signup and view all the answers

    What is the term for a heart valve that cannot close properly?

    <p>Regurgitation</p> Signup and view all the answers

    Which of the following conditions can cause a fourth heart sound due to ventricular stiffness?

    <p>Aortic stenosis</p> Signup and view all the answers

    Which of the following is NOT a characteristic of a fourth heart sound?

    <p>High pitched</p> Signup and view all the answers

    What is the primary structural difference between cardiac muscle fibers and skeletal muscle fibers?

    <p>Cardiac muscle fibers are branched.</p> Signup and view all the answers

    What role do intercalated disks play in cardiac muscle?

    <p>They enable cardiac muscles to contract as a single unit.</p> Signup and view all the answers

    Which structure serves as the pacemaker in the human heart?

    <p>Sinoatrial node</p> Signup and view all the answers

    What type of junctions are formed by gap junctions in cardiac muscle?

    <p>Adherens junctions</p> Signup and view all the answers

    What is the endocardium and its primary feature?

    <p>It's a smooth membrane lining the inner surface of the heart.</p> Signup and view all the answers

    How do impulses from the sinoatrial node communicate with the ventricles?

    <p>By passing through the modified cardiac muscle fibers of the conducting system.</p> Signup and view all the answers

    What is a physiological syncytium in cardiac muscle?

    <p>A structure formed by the fusion of adjacent cardiac muscle fibers.</p> Signup and view all the answers

    Which two portions compose the syncytium in the human heart?

    <p>Atrial and ventricular syncytium.</p> Signup and view all the answers

    What causes an increase in blood pressure during excitement or anxiety?

    <p>Release of adrenaline</p> Signup and view all the answers

    How does moderate exercise affect systolic pressure?

    <p>It increases by 20 to 30 mm Hg</p> Signup and view all the answers

    What happens to diastolic pressure during severe muscular exercise?

    <p>It decreases due to reduced peripheral resistance</p> Signup and view all the answers

    Which of the following is considered a central factor affecting arterial blood pressure?

    <p>Heart rate</p> Signup and view all the answers

    What is the primary mechanism for the rapid regulation of arterial blood pressure?

    <p>Nervous regulation</p> Signup and view all the answers

    What type of regulation adapts quickly but only lasts a short time in response to blood pressure changes?

    <p>Short-term regulation</p> Signup and view all the answers

    Which factor does NOT contribute to maintaining arterial blood pressure?

    <p>Carbon dioxide levels</p> Signup and view all the answers

    What component is NOT part of the vasomotor system involved in regulating arterial blood pressure?

    <p>Peripheral arteries</p> Signup and view all the answers

    Study Notes

    Structure of Cardiac Muscle

    • Cardiac muscle fibers have a branched structure
    • Intercalated disk is a tough, double-membranous structure at the junction between neighboring cardiac muscle fibers
    • Gap junctions facilitate rapid conduction of electrical activity from one fiber to another, making cardiac muscle fibers act as a single unit (physiological syncytium)

    Muscle Fibers and Pacemaker

    • Some muscle fibers are modified into a specialized structure known as pacemaker
    • Pacemaker fibers have less striation
    • Pacemaker generates impulses for heartbeat and is formed by pacemaker cells (P cells)
    • Sinoatrial (SA) node forms the pacemaker in the human heart

    Conductive System

    • The conductive system is formed by modified cardiac muscle fibers
    • Impulses from SA node are transmitted to atria directly and to ventricles through various components of the conducting system

    Endocardium and Blood Vessels

    • Endocardium is the inner layer of the heart wall, a thin, smooth, and glistening membrane formed by a single layer of endothelial cells
    • Endocardium continues as endothelium of blood vessels
    • Blood vessels are divided into arterial and venous systems

    Heart Sounds

    • Heart sounds are studied by stethoscope, microphone, and phonocardiogram
    • Abnormal heart sounds are known as cardiac murmurs, produced by changes in blood flow pattern
    • Cardiac murmurs are classified into three types: systolic, diastolic, and continuous

    Cardiac Output

    • Cardiac output is the amount of blood pumped from each ventricle
    • It is expressed in three ways: stroke volume, minute volume, and cardiac index
    • Methods used to measure cardiac output include Fick's principle, indicator dilution technique, thermodilution technique, ultrasonic Doppler transducer technique, Doppler echocardiography, and ballistocardiography

    Heart Rate

    • Normal heart rate is 72/minute, ranging from 60 to 80 per minute
    • Tachycardia is an increase in heart rate above 100/minute, occurring in physiological conditions like childhood, exercise, pregnancy, and emotional conditions, and in pathological conditions like fever, anemia, and cardiomyopathy
    • Bradycardia is a decrease in heart rate below 60/minute, occurring in physiological conditions like sleep and athletic heart, and in pathological conditions like hypothyroidism, heart attack, and congenital heart disease

    Arterial Blood Pressure

    • Arterial blood pressure is the lateral pressure exerted by the column of blood on the wall of arteries
    • It is expressed in four different terms: systolic blood pressure, diastolic blood pressure, pulse pressure, and mean arterial blood pressure
    • Normal systolic pressure is 120 mm Hg, ranging from 110 to 140 mm Hg, and normal diastolic pressure is 80 mm Hg, ranging from 60 to 80 mm Hg

    Physiological Variations in Arterial Blood Pressure

    • Age, sex, body built, diurnal variation, and emotional conditions affect arterial blood pressure
    • Arterial blood pressure increases after meals due to an increase in cardiac output and during exercise due to an increase in force of contraction and stroke volume

    Determinants of Arterial Blood Pressure

    • Central factors: cardiac output and heart rate
    • Peripheral factors: peripheral resistance, blood volume, venous return, elasticity of blood vessels, velocity of blood flow, diameter of blood vessels, and viscosity of blood

    Regulation of Arterial Blood Pressure

    • Arterial blood pressure is regulated by four mechanisms: nervous mechanism, hormonal mechanism, renal mechanism, and local mechanism
    • Nervous mechanism is rapid and operates through the vasomotor system, including vasomotor center, sympathetic and parasympathetic nerves, and blood vessels

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